YEONPYEONG ISLAND, South Korea — South Korea's marines commander Saturday vowed up to a "thousand-fold" retaliation for the North Korea artillery attack that killed four people just days earlier.

The threat came as efforts to halt violence in the region continued even as South Korea and the U.S. prepared to launch joint military maneuvers Sunday.

At a funeral in Seongnam, near Seoul, dignitaries and relatives placed white chrysanthemums at an alter for the two marines killed in Tuesday's attack on the South Korean island of Yeonpyeong. The attack was one of the worst bombardments of South Korea's territory since the 1950-53 Korean War.

The attack also killed two civilians.

About 600 mourners including Prime Minister Kim Hwang-sik and the marine commander Maj. Gen. You Nak-jun attended the funeral for the two marines at a packed gymnasium in a military hospital as somber music sounded.

"Our marine corps ... will carry out a hundred- or thousand-fold," retaliation against North Korea for launching Tuesday's attack, You said, without elaborating.

North Korea issued new warnings Saturday against the war games, calling them an "unpardonable provocation" and warning of retaliatory attacks that would "turn the stronghold of enemies into a sea of fire" if its own territory is violated. The comments ran on the state-run Uriminzokkiri website, and came a day after the North's warnings that the peninsula was on the "brink of war."

China, under pressure from the U.S. and South Korea to rein in its ally Pyongyang, urged both sides to show restraint while Washington played down the belligerent rhetoric, noting that the weekend war games were routine and planned well before last week's attack.

"The pressing task now is to put the situation under control and prevent a recurrence of similar incidents," Chinese Foreign Minister Yang Jiechi told U.S. Secretary of State Hillary Rodham Clinton by phone Friday, according to the ministry's website.

A dispatch Friday from Chinese state media saying Beijing's foreign minister had met the North Korean ambassador appeared to be an effort to trumpet China's role as a responsible actor and placate the U.S. and the South.

"The Chinese government is trying to send Pyongyang a signal that if they continue to be so provocative, China will just leave the North Koreans to themselves," said Zhu Feng, director of Peking University's Center for International and Strategic Studies.

Pressure on China
The Chinese statement came shortly after the release of a call by the top U.S. military officer for China to intensify pressure on North Korea and focus on leader Kim Jong-il's "vulnerabilities," saying that Beijing was wrong if it thought he was "controllable."

Admiral Mike Mullen, chairman of the Joint Chiefs of Staff, said in comments released on Friday that North Korea's nuclear ambitions increase the threat of regional instability.

"It's hard to know why China doesn't push harder," Mullen, told CNN television's Fareed Zakaria GPS, in comments due to air on Sunday. "My sense is they try to control this guy. And I'm not sure he is controllable."

He added: "I think we all have to focus on getting his attention — but in particular, China, in terms of focusing on his vulnerabilities and making sure that that part of the world doesn't come undone."

CNN released a transcript of the Wednesday interview.

The North's strike Tuesday destroyed large parts of Yeonpyeong Island in a major escalation of their sporadic skirmishes along the disputed sea border. The attack — eight months after a torpedo sank a South Korean warship, killing 46 sailors — has laid bare Seoul's weaknesses in defense 60 years after the Korean War.

South Korea's government has struggled to recoup from the surprise attacks, replacing the defense minister on Friday.

Drill 'not directed at China'
Beijing has warned against military acts near its coast as U.S. and South Korean forces prepared for four days of naval drills in the Yellow Sea starting on Sunday.

The U.S. military said the exercises, planned long before Tuesday's attack, were designed to deter North Korea and were not aimed at China. A Pengaton spokesman said it was "important" to state publicly that the exercises were "not directed at China."

The Pentagon is sending an aircraft carrier group led by the nuclear-powered USS George Washington for the maneuvers.

"We've routinely operated in waters off the Korean peninsula for years," said Captain Darryn James, a Pentagon spokesman. "These latest provocations have been by the North and they need to take ownership of those, not us."

"It's important for us to state publicly that this exercise and the ones we've done in the past are not directed at China," James said. "As with the previous exercises, these have been designed to strengthen deterrence against North Korea," he added.

North Korea has entered an unpredictable period of leadership transition with the elevation of Kim Jong-il's youngest son, Kim Jong-un, in September to the rank of general — in a clear sign he is the chosen successor.

Mullen has said he believes the artillery attack and the sinking in March of a South Korean warship, which the United States and South Korea blamed on the North, is likely linked to Kim Jong-il's "posturing" to allow the eventual succession.

But Mullen said the North Korean leader "is consistent and predictable only in his unpredictability," adding that Kim Jong-il should not be reward for his "bad behavior."

"He's not a guy we can trust," Mullen said. "That's why the leadership aspect of this from China is so important, because if any country has influence in Pyongyang, it's China," he said.

Fresh shots
James' remarks came shortly after fresh artillery shots were heard on the tense South Korean island of Yeonpyeong, three days after it was devastated by a North Korean attack and hours after Pyongyang warned that the peninsula was on the brink of war.

The blasts happened just after the top U.S. commander in South Korea, Gen. Walter Sharp, toured Yeonpyeong Island in a show of solidarity with Seoul and to survey damage from Tuesday's hail of North Korean artillery fire that killed four people.

The shelling by North Korea appeared to be a drill of its own with Reuters reporting that no shells landed in South Korea.

AP photographers at an observation point on the northwest side of Yeonpyeong heard about four explosions, and said they witnessed at least one flash of light on the North Korean mainland.

South Korea's YTN television network, citing an unidentified military official, said North Korea had fired up to 20 rounds. Yeonpyeong residents fled to shelters, the report said.

China has expressed concern over war games in waters within its exclusive economic zone, though the statement on the Foreign Ministry website didn't mention the joint South Korean-U.S. exercises.

That zone extends 230 miles from China's coastline and includes areas south of Yeonpyeong cited for possible maneuvers, though the exact location of the drills is not known.

China strongly protested an earlier round of drills in the region but has been largely mute over the upcoming exercises. Beijing could be withholding direct criticism to avoid roiling ties with South Korea and the U.S. and to register its displeasure with ally North Korea.

Only a few dozen residents remained on Yeonpyeong, with most of the population of 1,300 fleeing in the hours and days after Tuesday's attack and authorities urging them to evacuate.

Pyongyang's state news agency said U.S.-South Korean drills amount to a reckless move to target the North.

"The situation on the Korean peninsula is inching closer to the brink of war," the dispatch from the Korean Central News Agency said. "Gone are the days when verbal warnings are served only."

North Korea's army and people are "now greatly enraged" and "getting fully ready to give a shower of dreadful fire," the agency said. "Escalated confrontation would lead to a war, and he who is fond of playing with fire is bound to perish."

A North Korean official boasted that Pyongyang's military "precisely aimed and hit the enemy artillery base" as punishment for South Korean military drills — a reference to Tuesday's attack," KCNA reported in a separate dispatch.

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Earlier Friday, as Gen. Sharp toured Yeonpyeong, he walked down a heavily damaged street strewn with debris from buildings. Around him were charred bicycles and shattered bottles of soju, a kind of Korean alcoholic drink.

Sharp said that Tuesday's attack was a clear violation of an armistice signed in 1953 at the end of the three-year Korean War.

"We at United Nations Command will investigate this completely and call on North Korea to stop any future attacks," he told reporters on Friday.

Washington keeps more than 28,000 troops in South Korea to protect its ally from aggression — a legacy of the Korean War that is a sore point for North Korea, which cites the U.S. presence as the main reason behind its need for nuclear weapons.

Skirmishes between the Korean militaries are not uncommon, but North Korea's heavy bombardment of Yeonpyeong Island took hostilities to a new level because civilians were killed.

South Korean troops returned fire and scrambled fighter jets in response. Two South Korean marines and two construction workers were killed and at least 18 others wounded.

South Korea has said casualties on the North Korean side were likely significant, but none were immediately reported by the country.

North Korea does not recognize the maritime line drawn by U.N. forces and blamed South Korean military maneuvers near Yeonpyeong Island this week for the clash, calling them a violation of its territory.

The disputed waters have been the site of three other deadly naval skirmishes since 1999. However, the most costly incident was the sinking of a South Korean warship eight months ago that killed 46 sailors in the worst attack on South Korea's military since the war.

A South Korean border guard mans a post through a fence draped with re-unification ribbons near the border village of Panmunjom in Paju, South Korea, on Dec. 22, 2010. South Korea vowed Wednesday to "punish the enemy" as hundreds of troops, fighter jets, tanks and attack helicopters prepared massive new drills near the heavily armed border a month after a deadly North Korean artillery attack.
(Wally Santana / AP)
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A North Korean defector takes part in a candle light vigil on the eve of the one month anniversary of the North Korea's attack on Yeonpyeong Island in downtown Seoul, South Korea, on Dec. 22.
(Ng Han Guan / AP)
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A combination of photos shows North Korean soldiers taking part in a shooting exercise at a field in Kaepoong county, on the north side of the demilitarized zone (DMZ) separating the two Koreas, in this picture taken from south of the DMZ in Paju, about 31 miles north of Seoul, on Dec. 22.
(Jo Yong-hak / Reuters)
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Bae Bok-soon (R), an older sister of Bae Bok-chul, cries during the funeral for the two civilians who died when North Korea shelled Yeonpyeong Island on November 23, in Incheon, west of Seoul on De. 6.
(Jo Yong-hak / Reuters)
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Crew members watch as an F/A-18E Super Hornet lands on the deck of the aircraft carrier USS George Washington during a naval exercise with South Korea in the Yellow Sea on Tuesday, Nov. 30. The drills come amid heightened tension in the region after a North Korean artillery attack on South Korea's Yeonpyeong island last week.
(Park Ji-hwan / AFP - Getty Images)
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Staff watch radar screens in the Combat Direction Center on the USS George Washington during the military drills off South Korea.
(Wally Santana / AP)
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Former South Korean special agents whose mission was to infiltrate North Korea, sing a military song during a rally on the Yeonpyeong island, South Korea. About 85 former agents, who criticized the North's attack and urged the South Korean government to punish Pyongyang, landed the island Nov. 30 and said they would stay for a week to help with reconstruction.
(Lee Jin-man / AP)
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South Korean marines watch President Lee Myung-Bak's news conference on a television minitor on Yeonpyeong island on Nov. 29. Lee condemned North Korea's recent shelling of the South Korean border island, calling an attack against civilians an "inhumane" crime.
(Jeon Heon-Kyun / EPA)
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South Korean ships stage off the coast of South Korea's Yeonpyeong Island on Nov. 28 as war drills by the United States and South Korea began.
(David Guttenfelder / AP)
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South Korean protesters hold candles during a rally in Seoul opposing the military exercise between South Korea and the United States.
(Park Ji-hwan / AFP - Getty Images)
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South Korean women take cover inside a bomb shelter on Yeonpyeong Island after authorities sounded the alarm over a possible North Korean rocket attack on Nov. 28. It proved to be a false alarm.
(David Guttenfelder / AP)
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A North Korean soldier, right, looks back as she and another soldier patrol on a pathway along the bank of the Yalu River near Sinuiju, North Korea, Nov. 28.
(Andy Wong / AP)
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A South Korean police car is reflected in the shattered glass of a restaurant window along a seaside road on Yeonpyeong island on Nov. 27.
(David Guttenfelder / AP)
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Former South Korean marines burn images of North Korean leader Kim Jong Il, right, and his son Kim Jong Un, during a rally Nov. 27 in Seoul.
(Wally Santana / AP)
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Kim Oh-bock, mother of Seo Jung-woo, a South Korean marine killed in the Nov. 23 North Korean bombardment, cries as she holds his casket during a funeral service Nov. 27 at a military hospital in Seongnam.
(Ahn Young-joon / AP)
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South Korean protesters denouncing North Korean attack on an island close to the border between the two nations burn a North Korean flag in Seoul on Nov. 24. After North Korea's strike, South Korea and the United States said they would launch four-day naval exercises in the Yellow Sea involving an American aircraft carrier.
(Jung Yeon-Je / AFP - Getty Images)
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A picture taken off television shows the moment of impact of one of the artillery shells fired by North Korea onto the South Korean island of Yeonpyeong.
(Reuters TV)
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Related video

This picture taken by a South Korean tourist shows
huge plumes of smoke rising from Yeonpyeong Island in the disputed waters of the Yellow Sea on Nov. 23. North Korea fired dozens of artillery shells onto the South Korean island, killing two people, setting homes ablaze and triggering retaliatory fire by the South. It was one of the most serious clashes between the two sides in decades.
(AFP - Getty Images)
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Editor's note:
This image contains graphic content that some viewers may find disturbing.